1. Field of the Invention
The present invention relates to an improved process for the preparation of thiophosphoryl chloride that is useful as an intermediate for the synthesis of insecticidally active compounds.
2. Brief Description of the Prior Art
Disclosed by the prior art is a process for preparing thiophosphoryl chloride. British Patent 694,380 discloses the preparation of thiophosphoryl chloride by refluxing phosphorous trichloride and excess sulfur at atmospheric pressure, in the presence of carbon (activated with K.sub.2 S) and about 40 mole percent of thiophosphoryl chloride for about three hours. German Patent 1,145,589 discloses that PSCl.sub.3 is obtained by treating phosphorous trichloride and sulfur in liquid phase at atmospheric pressure, using Al or alloys thereof, preferably aluminum wastes, as catalyst. PSCl.sub.3 is preferably used as reaction medium and moderator. USSR 147,583 discloses that thiophosphoryl chloride is obtained from molten sulfur and phosphorous trichloride at 124.degree.-126.degree. C. and atmospheric pressure.